Group III-V compound semiconductor materials, such as GaN, AlGaN, etc., have many advantages, such as a wide and adjustable bandgap energy, and are thus widely used in optoelectronics and for electronic devices.
Particularly, light emitting devices, such as light emitting diodes (LEDs) or laser diodes (LDs), which use group III-V or II-VI compound semiconductor materials, are capable of emitting visible light of various colors, such as red, green and blue, and ultraviolet light owing to development of element materials and thin film growth techniques, are also capable of emitting white light with high luminous efficacy through use of phosphors or by combining colors, and have several advantages, namely low power consumption, semi-permanent lifespan, fast response speed, safety, and environmental friendliness, as compared to conventional light sources, such as fluorescent lamps and incandescent lamps.
Accordingly, application of the light emitting devices has been extended to transmission modules of optical communication means, light emitting diode backlights to replace Cold Cathode Fluorescent Lamps (CCFLs) which serve as backlights of Liquid Crystal Display (LCD) apparatuses, white light emitting diode lighting apparatuses to replace fluorescent lamps or incandescent lamps, vehicle head lamps, and traffic lights.
A molding unit protecting a light emitting structure or wires may be placed around a light emitting device, and light is refracted by the molding unit formed of a material, such as silicone, and thus the molding unit may function as a primary lens.
However, when the light emitting device is used a light source of a lighting apparatus, a secondary lens may be used to adjust a light emission path and the secondary lens is generally referred to as a ‘lens’.
A light path may be greatly changed according to materials of the lens, particularly, shapes of the lens, and, particularly, in an application, such as a streetlamp which causes light emitted from a light source to travel only in a specific direction, i.e., a forward or backward direction, the shape of the lens is more important.
FIG. 1 is a perspective view illustrating a conventional lens.
In the conventional lens, a refraction unit 110 and a reflection unit 120 may be arranged so as to be spaced apart from each other, the refraction unit 110 may refract light emitted from a light emitting device, and the reflection unit 120 may reflect light traveling rightward in FIG. 1 so that the reflected light travels leftward in FIG. 1.
The lens having the above structure may concentrate traveling of light on a specific direction but, if a plurality of light emitting devices is placed in a lighting apparatus, such as a streetlamp, a plurality of lens must be placed, when light sources are arranged, the lenses must be moved according to the light sources and, in this case, distribution of light emitted from the lenses may be greatly changed according to movement of the light sources and the lenses.